Project Summary/Abstract There is a critical unmet need for the application of new therapies to treat dry eye disease. A true aqueous- deficient dry eye due to inefficient lacrimal gland (LG) function is among the most common and debilitating clinical outcomes. Unfortunately, dry eye has no cure, and current treatment options target symptoms rather than resolving disease. A potential regenerative approach for restoring lacrimal function is stem cell therapy, where autologous stem/progenitor cells are transplanted into the injured organ or stem cells within the tissue are reactivated. However, to achieve this goal, we must identify LG stem/progenitor cells and understand how they are regulated. Our first objective is to resolve how nerves regulate LG homeostasis and regeneration by characterizing potential progenitor cells and determining how nerves control their differentiation into functional glandular tissue. Parasympathetic nerves regulate epithelial progenitor cells in other glandular systems, and are essential to the maintenance of lacrimal tissue. Yet, despite reduced innervation being a component of dry eye, the impact of nerve alterations on lacrimal gland homeostasis and repair (or on progenitor cells) is not known. Based on our preliminary data strongly suggesting the parasympathetic-nerve derived neuropeptide Y (NPY) is altered in patients with aqueous deficient dry eye disease (GWAS) and controls LG morphogenesis and tissue maintenance, we will test the hypothesis that NPY signaling regulates LG formation, homeostasis and regeneration by controlling stem/progenitor cell behavior. Our prediction will be addressed through 2 specific aims that seek to: 1) Define how NPY signaling regulates LG progenitor cells during development; and to 2) Determine the contribution of acinar progenitors and NPY signaling to adult LG homeostasis and regeneration. These aims will be achieved using a combination of human lacrimal glands and mouse genetics in conjunction with genetic, biochemical, immunochemical, and transcriptomic techniques. Our rationale for investigating this hypothesis is that understanding how progenitor cells are regulated during organ formation and after injury is critical if we are to repair, regenerate or replace the LG, and improve patient quality of life.